IUD Issues: Zero in with ultrasound
Sonographic evaluation of the positioning of an IUD is greatly enhanced by identification of the coronal view of the uterus, a plane that is not often obtainable using 2D imaging. Three-dimensional sonography allows visualization of the coronal view of the uterus with minimal post-processing manipulation of the uterine volume and is critical for determining malposition of an IUD.4-10
If an IUD cannot be visualized by 3D pelvic sonography, a secondary imaging procedure such as abdominal/pelvic x-rays or computed tomography may be necessary.10,11
Technique for coronal view
Abuhamad et al. have demonstrated the ease of attaining the coronal view of the uterus in a standardized fashion.12 To perform this so-called Z technique, follow these key steps:
• Obtain a midsagittal view of the uterus and magnify the image so that it includes the corpus and lower uterine segment. Obtain a 3D image and display it in a multiplanar view so that 3 orthogonal planes are on a single frame. Configure the display so that the A frame is the acquisition plane (sagittal view), the B frame is the transverse view and the C frame is the coronal view. A “reference dot” located at the same anatomic point in each plane is the rotational point around which the image is rotated (Figure 5A).
• Place the reference dot in the midpoint of the endometrial stripe in the sagittal plane of the uterus, which should be in the “A” frame.
• Using the Z rotation, manipulate the sagittal view of the endometrial echo so that it is horizontal (Figure 5A).
• Place the reference or marker “dot” in the midpoint of the endometrial stripe in the transverse plane of the uterus, frame B (Figure 5B).
• Using the Z rotation, manipulate the endometrial stripe so that the short axis of the transverse plane is horizontal.
• You should now see the mid-coronal plane of the uterus on the C frame (Figure 5B).
• Use the Z rotation to manipulate the image so that it is demonstrated in the conventional orientation.
• You can then display the image as a single plane for optimal evaluation.
The coronal plane can also be demonstrated with a rendering technique using the same principles. In that case, adjustment of the position of the endometrial echo in boxes A and B is identical; however, the render mode is used and the line of interest is placed over the endometrium (Figure 6).